The character renderer auto-switches finished one-shot animations to
STAND. MountFSM's jump/rear-up completion check only polled the current
timeline, so once the renderer swapped the mount to STAND the check read
a fresh STAND timeline, never reported completion, and the action state
stuck — leaving the horse gliding in a stand pose after jumping. Track
the animation each action requested and treat the instance playing
anything else as completion, matching the existing fidget logic.